Replacing Acros Blocklock on YT Decoy w/Taller Lower Headset "Cup" SOLVED

[bmxmarty]

4/10/24 Edit - I was able to ditch the Acros headset and get fork-to-down tube clearance with no steering limitations. Scroll down to reply #14 for explanation and photos.

I know this is headset-related question, but I'm specifically wondering if anyone has done this on a YT Decoy, because the clearance won't necessarily be the same as on other brands/models. In my case, it's a Decoy MX CORE 2 in size Large. Tight switchbacks are hard to deal with because of the Blocklock headset, but I know it's there to protect the downtube and fork from hitting when turned close to (or more than) 90-degrees. What I want to do is replace the lower cup (willing to buy an entire headset, of course) with a taller one so I get the clearance without the forced stop. In the late 90's and early 2000's I worked at a Santa Cruz dealer, and when building smaller sized Superlight's and Juliana's I'd use a sealed bearing Primo (BMX company) Gorrila lower headset cup in place of whatever came stock on the bike to get the needed clearance for the fork. That headset cup was designed to be beefy, but a side effect was that it had a taller stack height. Obviously modern frames don't use traditional 1-1/8" press-in headset cups, but hoping there's something out there that will do the trick. Thanks in advance for any info!

 

[TommyC]

Others have just chipped away at the block with a dremel to give you more angle. Also, Acros do a 120° and 150° block lock. Keep meaning to check my cube and see if I’ve got the 120, then might just try the 150

 

[bmxmarty]

Ha! Yeah, good call on the Dremel! If there wasn't a clearance issue (there actually may not be, I can't turn the fork far enough to verify, so am just assuming) I'd be all over that. I know Wolf Tooth makes a headset cup extender, and that plus a "normal" headset (or Dremeling the Acros) may be the solution, but I also can't find exact headset specs for the Decoy frame to ensure I actually find the correct parts... Insert my retro-grouch "Bikes were so simple back in the day" comment here. Appreciate your input Tommy!

 

[TommyC]

I’m resigned to the fact I’m stuck with the acros. I need the stop as don’t have the clearance. I emailed acros the other day to ask how you replace the bearings. You can’t. They’re pressed into the cups and need to be replaced as a whole.

 

[bmxmarty]

Yeah I saw that about the bearings on another post too. I wouldn't mind getting a slightly slacker head angle and minor increase in BB height with a cup extender, in exchange for losing the steering lock. If I figure out what (if anything) works as a replacement I'll post it here.

 

[TommyC]

I guess if you go slacker you get more clearance from the frame?

 

[bmxmarty]

If you use a headset cup extender or a taller lower headset cup, then provided that the increase in cup height is more than the overlap of the fork and the down tube, you'd have clearance and as a side-effect, also a slightly slacker head angle and minor increase in BB height. For example if there's 6mm (as an example, haven't measured the actual number) of negative clearance (overlap) where the fork hits the frame, and you use a 10mm taller lower cup, then you should have 4mm of positive clearance versus the 6mm of overlap. Then you could ditch the Acros without worry of smacking the fork into the frame. This is assuming that the Decoy uses a press-in lower headset cup (which it looks like it does), because on a frame like the Heckler for example, the bearings sit directly in the frame without a press fit cup, so the extender isn't an option. Model and size of the frame, along with fork model will all play into the exact clearance number, so it's a bit of a case-by-case situation. But my hope is that it will work.

 

[TommyC]

Is this not what you need?

Wolf Tooth Lower Headset Cup Extender - ZS - Zero Stack

This Wolf Tooth Precision Zero Stack (ZS) headset features Enduro stainless steel bearings and custom designed seals is for frames with internal bearing cups. These lower headset cup extenders allow you to adjust the geometry of your bike frame by increasing the effective fork length by 10mm.

www.wolftoothcomponents.com

 

[wenna]

Is this not what you need?

Wolf Tooth Lower Headset Cup Extender - ZS - Zero Stack

This Wolf Tooth Precision Zero Stack (ZS) headset features Enduro stainless steel bearings and custom designed seals is for frames with internal bearing cups. These lower headset cup extenders allow you to adjust the geometry of your bike frame by increasing the effective fork length by 10mm.

www.wolftoothcomponents.com

Damn that pricetag though!

 

[bmxmarty]

Is this not what you need?

Wolf Tooth Lower Headset Cup Extender - ZS - Zero Stack

This Wolf Tooth Precision Zero Stack (ZS) headset features Enduro stainless steel bearings and custom designed seals is for frames with internal bearing cups. These lower headset cup extenders allow you to adjust the geometry of your bike frame by increasing the effective fork length by 10mm.

www.wolftoothcomponents.com

Yup - that is it. I just heard back from Wolf Tooth this AM to confirm the fit, because YT doesn't list spec details about the headtube. Using this should do the trick. Since it adds 10mm to the bottom of the headtube, I'll need to remove 10mm of spacers from the top, but overall bar height won't really change. I'll post back once I get it installed. Appreciate your input Tommy!

 

[bmxmarty]

Damn that pricetag though!

I just confirmed with Wolf Tooth that it's actually a full lower "Premium" headset assembly, complete with a race and a stainless bearing. So it's actually a great deal for what is basically half of a high-end headset, that also happens to be a solution to the Acros problem. Wolf Tooth calling it an "Extender" makes it sound like it's just a machined aluminum piece that goes between the frame and the lower headset assembly, which is confusing. Stay tuned for how this works out!

 

[E-MAD MALC]

I just confirmed with Wolf Tooth that it's actually a full lower "Premium" headset assembly, complete with a race and a stainless bearing. So it's actually a great deal for what is basically half of a high-end headset, that also happens to be a solution to the Acros problem. Wolf Tooth calling it an "Extender" makes it sound like it's just a machined aluminum piece that goes between the frame and the lower headset assembly, which is confusing. Stay tuned for how this works out!

Is your steerer tube still going to be long enough just a thought

 

[bmxmarty]

Is your steerer tube still going to be long enough just a thought

It is, I'll just need to pull two headset spacers out. That had been one of my first thoughts too, since bikes tend to ship with very few spacers and a pretty short steerer tube. Good looking out though, thank you!

 

[bmxmarty]

I got this resolved, and have decided to bore you with more details than you ever wanted. I replaced the Acros Blocklock headset with a Wolf Tooth, so now have no steering restriction, and the fork will not hit the down tube when turned 90-degrees. I really only needed the taller lower headset cup (the Wolf Tooth "Extender" as mentioned by TommyC), but decided to replace the upper headset assembly as well. I went for the Wolf Tooth "Premium" set-up (the lower assembly is also the "Premium" version, though they don't specifically say that), because I can't stand janky headsets, and buying a high-quality one generally means you never have to think about it again. Your bike spec could vary, so double-check with YT, but in my case for the YT Decoy MX CORE 2 in a size large (different frame sizes will likely have different levels of clearance) here are the parts I bought. Wolf Tooth part numbers are listed as well:

Upper: Wolf Tooth Premium ZS Headset - Zero Stack. Upper / ZS44/28.6 6mm Stack / Black. SKU: ZS44U-5MM-BLK.
Lower: Wolf Tooth Lower Headset Cup Extender - ZS - Zero Stack. ZS56/40 Lower Headset Extended 10mm / ZS56 / Black. SKU: ZS56L-40-BLK-P10.

As E-MAD MALC mentioned, adding 10mm to the bottom of your headset height means you'll lose 10mm at the top, so make sure you've got enough steerer tube length to be able to do this modification. My Acros top cap is 16mm tall, so I chose the 6mm Wolf Tooth top cap height option to exactly offset that. I'm still running two headset spacers under the stem, just as before. I am not using the Wolf Tooth stem cap with the integrated 5mm spacer, as I wanted the height under the stem, so just used a standard stem cap.

Both sides of the fork have ample clearance to the down tube, and the head angle should have slackened by less than half a degree. If memory serves, raising your front end by 25.4mm (one inch) will slacken your head angle by about 1-degree.

In terms of installation, you will need some pretty specific tools, so while you can MacGyver it without them, I'd recommend having a shop do the install unless you're capable and equipped with the proper tools. I was a mechanic for many years, so have the tools, and even still I managed to blow up the lower bearing during the removal process. That was not due to a lack of quality by Acros, it was totally my bad. I should have removed the upper headset cup first, to prevent the headset removal tool from being restricted by the inner diameter of the upper bearing, which meant it couldn't expand all the way. That caused it to sit on lower bearing instead of the cup, so it blew up. Here's the tools I used that were specific to the headset, you'll also need Hex and/or Torx tools to take your front end apart:

Park RT-2 for the lower cup removal.
Park RT-1 for the upper cup removal.
Park CRP-1 (link is for the CRP-2, as mine doesn't exist anymore) to remove the headset race.
Park CRS-15.2 to install the new headset race.
Park HHP-2 to install the new headset cups.

Thanks to the folks who chimed in on this post, I appreciate it!

 

[FixThatBike]

Thanks for this post! This is awesome info. I'm curious if you notice the bike handling any differently with the slacker head angle. I'd love to hear a report after you've gotten in a couple rides on it.